The Seismograph

            The seismograph. When I say what word, what do you think of? Maybe you think of a type of graph that is used in math. Well, you’re on the right track. A seismograph is an instrument used for detecting and measuring the intensity, direction, and duration of an earthquake. Chinese astronomer, Chang Heng invented the first seismograph in A.D. 132, but he called it the seismoscope. John Milne invented the modern seismograph, which is used all over the world now, in 1880. The modern seismograph is a heavy weight fastened to a horizontal rod, while the rod hangs from a pole, and is free to swing side to side, like a pendulum. At the end of the rod is an ink pen, and directly underneath that is a piece of paper rolled around a cylinder. The cylinder rotates so the pen continuously draws a line, and when the ground shakes, the line is zigzagged. The stronger the shaking, the sharper the zigzags. This zigzag trace records and shows the varying amplitude of ground alternation beneath the instrument. They also detect seismic waves, or vibrations. The picture made by a seismograph is called a seismogram. Did you know that some seismographs have been transported to the moon, Mars, and Venus? The seismograph is like the Richter Magnitude Scale, because they both have the same purpose. In conclusion, seismographs are very important instruments used to detect earthquakes, and without them, we would never know when to expect one.  

                                                          First Seismograph ^                                                                  

                                                                   ^Modern Seismograph^

Sources:

http://www.thetech.org/exhibits/online/quakes/seismo/

http://school.discovery.com/studystarters/facts/earthquakes_firstseismograph.html

http://inventors.about.com/library/inventors/blseismograph.htm

http://scign.jpl.nasa.gov/learn/eq7.htm

http://cse.ssl.berkeley.edu/lessons/indiv/davis/inprogress/QuakesEng3.html

http://www.seismo.unr.edu/ftp/pub/louie/class/100/seismic-waves.html

http://web.mit.edu/invent/iow/milne.html